This invention relates to apparatus, systems and methods for converting energy present in ocean surface waves into electric energy.
Known wave energy converter (WEC) systems for capturing ocean surface wave energy include: (a) a first component (also referred to herein as a “shell” or “vessel” or “float”) which, when placed in a body of water, is designed to move up and down, generally, in phase with the waves in the water and thus absorb and/or release energy; (b) a second component (also referred to herein as a “shaft”, “spar”, “column” or piston) which is either stationary or moves generally out of phase relative to the waves and the first structure; and (c) a power take off (PTO) device coupled between the first and second components which, in response to the relative motion between the first and second structures, is designed to produce electrical energy.
Due to the forces of the waves there tends to be twisting and turning (rotation) of the shell relative to the column when the WEC is in the water. That is, the body of water applies forces to the shell and column which tend to cause the shell to rotate or twist about the column (in addition to the desired vertical, up and down, motion). The twisting or rotational motion is potentially damaging and is highly undesirable.
A prior art solution for preventing twisting of the column 12 relative to the shell 10 is shown in FIG. 1. The top of the column is shown connected to a cross-shaped buffer 103 with vertical anti-rotational pipes 101 being located between the arm of the cross, at or close to their junction, to prevent rotation. Incorporating such restraining members adds to the complexity and cost of the design and still allows for some twisting along the column, if the anti-rotation mechanism is only introduced at one end of the column.